obamawassworn in for the first time in 2009. dan bonngeno was the leadsecretserviceagentas people packed the national mall in downtown d.c. a potential terrorist could have been hiding in plain sight. >> you can't guarantee anything. you reduce the probability to hopefully something minuscule so if something happens your response is enough to keep casualties to a minimum n times square 2010. a car bomb failed to explode and was disarmed before it could hurt anyone. two days later a pakistani-american was caught trying to board a flight to the middle east. big sporting events like the boston marathon had been viewed as inviting targets since 9/11. the marine corps marathon attracts 30,000 runners each year. super bowl organize ohhers are often criticized for too much security at the big game. and securing every possible public event that could invite an attack is respond reasonable. michaelle leiter was the counter terrorism director under president george w. bush. >> you can't protect all of the people at all of the large sporting events or any public gathering. that's the advanta

as possible.presidentobamawilltravel here to boston on thursday for a religiousinterfaceservice, dedicatedto the three people killed in the attack and the more than 180 people injured. we now know the name of another of the three people who died, her name krystle campbell, 29 years old. her mother spoke out a little while ago in tears, saying she and her family are heart broken. we also just learned that the third person who died was a boston university graduate student. investigators here in boston say their hunt for a terrorist -- for a suspect in these terror bombings is still preliminary, and this case, they say, is wide open. >> among items partially recovered are pieces of black nylon, which could be from a backpack, and what appeared to be fragments of bbs, and nails, possibly contained in a pressure cooker device. in addition, this morning, it was determined that both of the explosives were placed in a dark colored nylon bag or backpack. the bag would have been heavy because of the components believed to be in it. >> let's bring in our chief national correspondent john